SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e39aee4fed30959efd847da1d6dea542fe728159900f75f88c51f5f6de95c4d3' 
  AND token = 'zxYhenUO1RPAObwP1qH2dO8E1kPKOfj12kjP2PegQFs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}